The present invention relates systems and methods for optimizing parameters of hardware for audiological devices. More specifically, the present invention relates to systems and methods in which acoustic waves are transformed into electrical signals in a device, and the settings of the device are tailored to the individual.
Programming hardware for audio signals is complicated due to the complexity of audio signals. In addition to the basic problems associated with reproducing a constantly changing sound comprised of an overlapping collection of various pitches and amplitudes, problems are compounded by signal to noise issues, threshold hearing variances across a wide range of the spectrum in which humans can hear, and other unique factors. With such a complex variable set, or from another perspective, such a wide optimization space, it is difficult for a user or operator to arrive at an optimized setting.
For example, cochlear implants include technology that transforms complex auditory waves into pulses to be sent to a plurality of channels on the inner cochlea of a patient in order to stimulate the neurons on the select channels. The process of transforming auditory waves into electronic signals requires the transformation of a multitude of information including frequency, amplitude, and voltage among background noise and environments into an electrical signal to recreate hearing.
Cochlear implants are neural prostheses that help severely-to-profoundly deaf people to restore some hearing. Physically, three components can be identified: the speech processor with its transmission coil, the receiver and stimulator, and the cochlear implant electrode array. The speech processor receives sound from one or more microphones and converts the sound into a corresponding electrical signal. While the hearing range of a young healthy human is typically between 0.02 and 20 kHz, it has been assumed for coding of acoustic information in cochlear implants that most of the information used for communication is in the frequency range between 0.1 and 8 kHz. The frequency band from 0.1 to 8 kHz is divided into many smaller frequency bands of about 0.5 octaves width. The number of small frequency bands is determined by the number of electrodes along the electrode array, which is inserted into the cochlea. Each frequency band is then treated by a mathematical algorithm, such as a Hilbert transform that extracts the envelope of the filtered waveform. The envelope is then transmitted via an ultrahigh frequency (UHF) connection across the skin to a receiver coil, which was surgically implanted behind the ear. The envelope is used to modulate a train of pulses with a fixed pulse repetition rate. For each of the electrodes, a train of pulses with fixed frequency and fixed phase is used to stimulate the cochlear nerve. Multiple algorithms have been implemented to select a group of 4-8 electrode contacts for simultaneous stimulation.
Damage of cochlear neural structures can result in severe deafness. Depending on the neural degeneration in the cochlea performance, the performance of a cochlear implant user may vary. Changes that occur include the demyelination and degeneration of dendrites and neuronal death. The neuronal loss can be non-uniform and results in “holes” of neurons along the cochlea. Holes lead to distortion of the frequency maps, which affects speech recognition. Caused by changes in myelination and synapse size, changes in firing properties of the nerve were described such as prolonged delay times and changed refractory periods. In the brainstem and midbrain the neuronal connections appear to remain intact. However, a decrease in neuron size, afferent input, synapse size and density can be detected. Neural recordings reveal a change in response properties that adversely affect temporal resolution such as elevated thresholds, de-synchronization, increased levels of neural adaptation, increased response latencies. A loss of inhibitory influences has been described. At the cortex, spatially larger cortical activation was seen with (PET). The findings support a plastic reorganization and more intense use of present auditory networks.
A conventional cochlear implant includes a speech processor that transforms the acoustic waves received on the microphone into an electrical signal that stimulate the implanted electrode array, and consequently, the auditory nerves. Auditory waves are a complex summation of many different wave forms, and the processor decomposes the complex auditory signal received on the microphone into discrete component frequencies or electrical pulses to be sent to the auditory neurons through the electrodes. Nerve fibers in the vicinity of the electrodes are stimulated and relay information to the brain. Loud sounds produce high-amplitude electrical pulses that stimulate a greater number of nerve fibers, while quiet sounds produce low-amplitude pulses effected a lesser number of nerve fibers. Different variables within the software on the processor affect the output of the cochlear implant speech processor.
To activate the cochlear implant, an audiologist tunes the levels and stimulation parameters of the speech processor so that the sounds picked up by the microphone are heard at the individual's ideal loudness level. Initially, the audiologist stimulates the implant's channels or electrode pairs with small electrical pulses to test whether the user hears the stimulus. Over the course of subsequent sessions, the audiologist performs a series of tests to understand the user's listening needs. The user's cochlea is tuned to perceive different pitches depending on the area being stimulated. During the sessions, the audiologist stimulate the implant's channels to simulate pitch differences. The audiologist will also vary the electrical current on each channel to find the most comfortable loudness level. The audiologist may also take threshold measurements to understand the user's softest level audible on each channel. The audiologist ultimately generates a map that is downloaded to the speech processor to enable the processor to appropriately adjust volume levels based on the individual's needs.
With cochlear implants and other hearing devices, each patient is unique. Following implantation, changes occur that can affect performance of the device. Changes include genetic disorders, iatrogenic procedures, ototoxic drugs, or loud noise exposure. The user's hearing will change over time, requiring additional visits to the audiologist in order to rerun the tests and adjust the map accordingly.
Additionally, hearing devices other than cochlear implants, such as recent hearing aid technology, may require programming based on audiological feedback during testing to achieve optimal results. The latest generations of hearing aids and other “hearables” include parameter settings for amplification, compression, noise rejection/cancellation, etc. Being able to fine tune each of the parameters, in each ear, provides even greater flexibility in the optimization of these devices. However, the complexity created by the many parameters can be a challenge for manual tuning.
Accordingly, there is a need for an optimization system for effectively adjusting a large number of parameters of a hearing device while accounting for a variety of hearing situations.